Method of washing coal



METHOD OF WASHING GOAL Filed Dec. 25, I935 I f l4 1 38 "39 I I3 12 a 37a2 2 [9 f 2 22 2| 4 33 35 26 f 1 2 LINE I r41 TO SETTLING TANK 42 TOREFUSE PIT Maw

INVENTOR Patented June 25, 1940 UNITED, STATES PATENT OFFICE 2,205,942METHOD or WASHING GOAL 1' Walter M. Cross, In, Kansas City, Mo.-Application December 23, 1935, Serial No. 55,807

4 Claims. (01. 209173) This invention relates to an improvement in theart of coal washing.

On object of my invention'is ,the utilization ofa colloidal clay, suchas Wyoming bentonite, 5 which is of such high colloidal emciency that itis capable of forming a highly viscous and substantially stable aqueoussolution when-it alone is combined with many times its weight of waterfor washing coal and separating the impurities 1o therefrom by virtueofthe viscosity of said solution, which maintains the pure coal insuspension, while the impurities settle out. V Another object of myinvention is to teach a method of floating coal to segregate it from thei5 refuse primarily by the viscosity of the washing medium attained byaddition of Wyoming-type bentonite to the water of the washing medium'.

instead of the specific gravity thereof, but I may also add aweightingagent to increase the specific m gravity of the washing medium, and saidweighting medium will be held in suspension by the Wyoming bentonite. I

These objects are accomplished by providing a method of washing coalwhich provides for new I types of washing medium, the viscosity of whichis depended upon to separate the coal from the.

refuse instead of the specific gravity of the said medium. The followingdescri tion shows in detail one form of apparatus t t may be used toaccomplish my results.

The drawing is a partially cut-away side elevation of a coal washer.

In the drawing, I is the coal intake chute; 2 is the washing receptacle;3 is the paddle wheel agitator located in the washing receptacle; 4 isthe bearing for the paddle wheel shaft; 5 is the paddle wheel shaft; 6isa pulley fixed to the paddle wheel shaft and is driven by belt I whichin turn is driven by power source 8; 9 is the discharge hp of thewashing receptable; I0 is the spraying and. dewatering screen; H is thewater spray line for washing'ofi the solid matter which has beenleft-onethe coal by the wash-- ing medium; I2 is the bulb of a floatcontrol,

the arm I4 of which pivots vertically around bearing l3; I5 is, amercury electric switch which closes a circuit whenthe mercury hasflowed to the end of the bulb containing the electric terminals in suchmanner as to cover m both terminals; 16 is an electric valve for fluid:v

I1 is a fluid line so located as to empty fluid into receptacle 2 whenvalve I6 is open; It! and l9 are flexible tubes which allowgthe washingmedium contained in receptacle 2 to flow through -weighing box 20; His aknife edge supporting weighing box 20; 22 is the beam of' a scalemechanism supported on fulcrum 23; 24 is a weight movable on beam 22; 25and 26, are sep- -arate. sets of electric terminals in a mercury Ielectric switch bulb; 21 is the discharge line b for the washing medium;28 is an electric valve located in line 21; 29 is an electric valvelocated in discharge pipe 3| of hopper 30; 32 isa float suitablysupported by a horizontal bearing in arm 33 which arm pivots verticallyabout bear- 10 ing 34; 38 is a cylinder in which piston 31 is movedvertically in such a manner as to give arm 33 a vertically reciprocatingmotion through bearing 35; 39 is an air supply line into cylinder 38; isa pipe connection between cylinderof discharge I15 9 with water. Whilepaddle 25 wheel 3 is rotating, a gelling material namely, bentonite, isslowly added. The most eflicient substance to use is a clay known asbentonite, of the Wyoming variety. This clay has the characteristic offorming a gel with from fifteen 30 to twenty-five times its weight ofwater, and the clay may be chemically treated to be even more efllcientin gelling power. The gel is most easily formed when the bentonite is ofsuch fineness that it will pass a screen, having 200 meshes to the inch.The gel formed by treated bentonite gives a washing medium having aviscosity'of any desired amount up to 180 centipoises with only 5.5percent, by weight, of solids concentration. Such a gel is thixotropicin char- 40 acter. If agelling agent such as Wyoming bentonite is used,the amount of clay placed in thewater may range from M; of 1 percent to15 percent, by weight, of the water present.

Where there is not an appreciable amount of flre clay brought into thewashing medium by the coal, the viscosity of the gelled washing mediumalone or in conjunction with the upward component given the washingmedium in recep tacle 2 will be suflicient to properly float thecoalvfrom the washer.

As the coal is floated in the washing medium contained in receptacle 2there are separated from it foreign materials such as flre clay, pyrltesand shale. These materials, particularly the last 86 and the cleanedcoal floats off through discharge lip 9. A sharp spray of water isplayed upon the coal as it passes on to screen [0 and then vibration ofscreen Ill, subsequently passed, dewaters the coal. From screen I thecoal goes to further processing means or is loaded out as the case maybe.

Float 32 is given a continual reciprocating motion vertically by arm 33which pivots around horizontal bearing 34. Through line 39, intermittentair impulses continually force piston 31 dowpnwardly. This mechanismisso designed that the weight of float 32 tends to keep piston 31 towardthe top of cylinder 38. The action of piston-31 through piston rod 36 onarm 33 is to give float 32 a constant vertical reciprocating motion. Airline 40 .enters cylinder 38 at a point which is just above the top ofpiston 31 when it is at the bottom of this cylinder. Piston 31 does notmake the full vertical traverse of the cylinder at each air impulsethrough line 39 but travels only a short distance downwardly. As refusebuilds up in the bottom of receptacle 2, float 32 assumes a higher meanlevel with respect to the bottom of the receptacle, since it isconstantly jigging up and down and at the bottom of each stroke rests onthe refuse in the bottom of the receptable. As the level of the refusebecomes higher, piston 31 attains a lower mean levelgwith reference tothe bottom of cylinder 38 until the air from line 39 passes throughcylinder 38 into line 4|! and passes thence to valve 42. Valve 42 isopened by the air pressure thus resulting and the refuse in receptacle 2is discharged through line 4| to a refuse pit, from which some light mudmay be reclaimed.

As washing continues, it may be desirable when using a weighting agentto maintain the specific gravity of the washing medium relative to theviscosity within certain limits. To accomplish this the washing mediumis continually circulated through lines l8 and I9 into weighing box 20which is thus kept full. I If the specific gravity of the washing mediumbecomegreater than the desired value, box 28 will increase in weight andwill depress knife edge 2|. This causes beam 22 to turn on knife edge23, raising the end of the beam where is located the mercury electricswitch. This tipping of arm 22 causes the mercury in the switch to flowso as to cover electric terminals 25, thus closing an electric circuitwhich causes valve 28 to open and allows the washing medium to flow fromreceptacle 2 through line 21 to the settling tank. When the specificgravity of the washing medium falls to the desired value, box 20 willdecrease in weight and will turn beam 22 about knife edge 23 so that themercury in the mercury electric switch uncovers terminals 25 whichaction closes valve 28. It is sometimes desirable to combine lines 21and 4| and todischarge tea single pit or tank, either when the refuselevel in receptacle 2 rises to a predetermined heigh or when thespecific gravity of the washing me um reaches a predetermined maximum.At the same time, since the level of the washing medium in receptacle 2is becoming lower, float bulb l2 will also become lower and cause themercury in switch .l! to cover the terminals therein. These terminalsclose an electric circuit which opens valve l8 allowing washing mediumwhich has been cleared in the settling tank, or water, as may bedesired,'to flow into receptacle 2 until the level of the medium in thereceptacle is high enough to break the contact in switch 13 which thuscloses valve ii.

If the specific gravity in receptacle 2 falls below the desired value,the weight of box 28 decreases. This allows arm 22 to tip on knife edge23 in such a manner as to run the mercury in the mercury electric switchattached to said arm 22 to flow over terminals 23 which closes anelectric circuit to valve 28. with valve 28 open, additional solidmatter is allowed to flow into receptacle 2 through pipe 3| until theweight of box 20 has increased sufficiently to break the contact onterminals. when valve 23 closes.

In this manner thespeciflc gravity of the washing medium is kept withinthe desired limits'relative the viscosity.

Further advantages of this invention by adding a gelling material havingthe properties of Wyoming bentonite are that the flre clay washed fromthe coal can be supported in greater quantities in the washing medium,thus more emciently supporting the coal therein and also preventing thefire clay from settling in a hard mass in the bottom of the washingreceptacle which causes a shut-down and requires constant cleaning.

It is apparent that various changes may be made in this invention withinthe scope of the appended claims.

What is claimed is:

1. The method of washing coal which comprises introducing raw coal intoan aqueous medium consisting of water and Wyoming bentonite and having aspecific gravity less than that of coal and having a viscosity whichsubstantially floats the coal alone and creating a circulating movementin the aqueous medium to an extent such that the coal is held insuspension while the impurities associated with the coal sink to thebottom of the aqueous medium.

2. The process as set forth claim 1 in which the circulating movement inthe aqueous medium is effected by agitation.

3. The process as set forth in claim 1 in which the amount of Wyomingbentonite is from to 15%.

4. Theprocess as set forth in claim 1 in which the aqueous medium isprepared by adding a Wyoming bentonite having a fineness such that itwill all pass through a 200 mesh screen, to

,water, the amount of bentonite being from V to 15%. l

. WALTER -M. CROSS, JR.

